Convert "Existing" Mesh to Bmesh (AttributeError: module 'bmesh' has no attribute 'from__mesh')
A changed the way you selected active object and the way bmesh.from_mesh was called.

from os import system
   system("cls")

import bpy 
import bmesh

#Assign object as a part of the active scene
scene = bpy.context.scene
ob = bpy.context.object
vert = ob.data.vertices

#Set default mode == Edit 
if bpy.ops.object.mode_set.poll():
    bpy.ops.object.mode_set(mode='EDIT')

print("Active object = ",ob.name)

#Store selected vertices in a list
print("vert_selected")
#ob = bpy.context.object #Also direct context assignment raised no attribute error
me = ob.data
bm = bmesh.new()         # Create a new bmesh container instance
bm.from_mesh(me)         # Pass your mesh into this container

vert_selected = [v.co for v in bm.verts if v.select]   
for vs_s in vert_selected:
    print(vs_s)


bpy.ops.mesh.select_all(action='DESELECT')
bm.select_flush(True)

bpy.ops.object.mode_set(mode='OBJECT') # if bmesh.from_edit_mesh() --&gt; mode == EDIT - ValueError: to_mesh(): Mesh 'Cube' is in editmode 

bm.to_mesh(me) #If mode ==Object  -&gt; ReferenceError: BMesh data of type BMesh has been removed
bm.free() 
ob.update_from_editmode()
```